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Chest radiograph — enlarged cardiac silhouette
Plain radiograph · Posteroanterior · Thorax
Before you comment on anything
The value of this film for a first-year student is not the diagnosis; it is the measurement. The cardiothoracic ratio is one of the few numbers in radiology you can take off a film with a ruler, and it only means anything if the projection is right. Prove the film is posteroanterior, then measure, then speak.
Plain radiograph · Posteroanterior · © MedpulseIq.com
Read it in order
0 of 8
Work down the list. The answer unlocks when you have been through all of it.
Landmarks to name
Right heart border
To the right of the midline, above the right hemidiaphragm
Formed by the right atrium — this is the border you measure from.
Left heart border
To the left of the midline, curving down to the apex
Formed mainly by the left ventricle, with the left atrial appendage and pulmonary trunk above it.
Widest internal thoracic diameter
Between the inner margins of the ribs at the level of the diaphragm
The denominator of the cardiothoracic ratio.
Cardiac apex
The lowest, most lateral point of the left heart border
Its position tells you whether the heart is displaced or enlarged.
Viva voce
1 of 5 · 0 answeredSay your answer out loud before you open it. That is the exam skill.
How is the cardiothoracic ratio measured?
Senior’s 30-second takeaway
Chest radiograph — enlarged cardiac silhouette — the whole bench in four lines. Read this on the way in.
- If you see this
- A chest film in the posteroanterior projection · A cardiac shadow spanning more than half the chest · Crisp heart borders against aerated lung
- If asked to identify it
- On this adequate posteroanterior film the cardiothoracic ratio is greater than one half.
- If asked one more
- The right border is right atrium and the left border left ventricle.
- If asked why it matters
- The plain film cannot distinguish chamber enlargement from a pericardial effusion; echocardiography does.
Then stop. Let the examiner ask the next question.